A light emitting diode generally emits light having a peak wavelength of a narrow full width at half maximum and thus requires a plurality of active layers, which emit light in various wavelength bands, in order to realize white light. However, such a light emitting diode including a plurality of active layers provides very low fabrication efficiency for technical and process reasons. Accordingly, in order to realize a while light emitting device using a light emitting diode, the light emitting device further employs phosphors that excite light emitted from the light emitting diode into light having a different wavelength band than that of the emitted light. As a result, white light can be obtained through combination of light emitted from the light emitting diode and light excited by the phosphors.
For example, phosphors, which absorb part of blue light as excitation light to emit yellow green light or yellow light, can be deposited onto a blue light emitting diode to obtain white light. However, since a white light emitting diode package with this structure employs luminescence of yellow phosphors, the white light emitting diode package has low color rendering and low color reproducibility due to depletion of spectrum in green and red wavelength regions of light emitted therefrom. Accordingly, this type of light emitting device has a limit in application to the field of illumination or display. To overcome such a problem, a light emitting diode is fabricated using a blue light emitting diode chip and phosphors that emit green light and red light using blue light as excitation light. That is, it is possible to realize white light having a high color rendering index through combination of blue light with green light and red light excited by the blue light.
However, for a conventional light emitting device using a blue light emitting diode chip, blue light having a peak wavelength of about 450 nm has relatively high intensity. The blue light having such a peak wavelength can cause various malfunctions such as deterioration of eyesight or sleep disturbance, and the like. In Particular, the blue light emitting diode applied to lighting apparatuses and the like can cause severe problems.
In order to realize white light, a UV light emitting diode chip can be used instead of the blue light emitting diode chip. However, since the UV light emitting diode chip emits light of wavelengths having relatively high energy, there can be problems of decomposition of an encapsulation material, discoloration and deterioration of a lead frame, and the like. In addition, although the encapsulation material can be prepared using materials (for example, methyl silicon) that exhibit relatively high resistance to UV light, such materials have low mechanical reliability due to high hardness. Moreover, UV light emitted from the UV light emitting diode is not favorable to humans or animals.